Welding of low alloy steel



United States Patent WELDING 0F LOW ALLOY STEEL Gilbert R. Rothschild,Berkeley Heights, and Sibley, New Providence, N. J., assignors to AirReduction Company, Incorporated, New York, N. Y., a con poration of NewYork No Drawing. Application May to, 957, Serial No. 659,474

Claims. (Cl. 219137) This invention relates to the inert-gas-shielded,electric arc welding of certain low alloy steels, such as armor plate.This application is a continuation-in-part of application Serial No.444,396 filed July 19, 1954, now abandoned.

Armor weldments, such as welded military tanks, are customarily obtainedby using stick electrodes and an electric arc process. In this type of aweld, it is necessary to obtain high yield strength so that the strengthof the weld will approximate or match the strength of the armor. It isalso necessary, of course, that the armor welds are able to resist theimpact of shells, especially at low temperature, so that a tank will notbe split open by an oblique hit with obvious consequent hazards. Similarconsiderations are involved in other armor constructions, such asbattleships. After trying and extensively using expensive stainlesssteel stick electrodes which did not give the desired yield strength inthe weld, specially-coated ferritic-type stick electrodes were developedand used. However, it was found that a great amount of care had to beexercised in fabrication and during welding in order to avoid the dangerof latent defects in welds which would result in cracking in the welds,especially at low temperatures. Thus, subsequent to World War II, it wasnecessary to take extreme precautions with the ferritic-type electrodes,such as using shipping cans, in order to prevent, for instance, waterfrom being retained in the electrode coating. Another precautioninvolved the use of an electrode baking oven at the welding location asa final assurance that undesired moisture was not retained in thecoating.

It is the primary object of the instant invention to provide an improvedmethod and means for welding certain low alloy steels, such as armor, bywhich cheaper, high-strength welding is effected and the above-mentionedcracking problem is avoided.

A recently-developed, low alloy steel, commonly referred to as T-steel,which is a U. S. Steel plate material identified more specifically byT-l, has excellent mechanical properties which are obtained through acritical balance of small amounts of alloying elements (manganese,nickel, chromium, molybdenum and boron) and a .quench-and-temper-heattreatment, after hot rolling. The exceptional mechanical properties,namely high yield strength, and low-temperature impact strength, and therelatively low cost are expected to result in widespread use of thisT-steel for welded pressure vessels, rolling stock, and the like. It hasbeen conventional practice to weld standard steels with coated stickelectrodes or with a flux-submerged arc, neither of which are consideredideal for welded T-steel constructions. The coated electrodes involveproblems such as the above-mentioned cracking difiiculty. The submergedare inherently has the problem of providing the flux and poorvisibility. It is, of course, highly desirable that the welding of thisnew T-steel by an improved, faster welding method and means, other thanmethods involving coated stick electrodes or a flux-submerged are, beaccomplished.

Another object of the instant invention is the provision of an improvedmethod and means for welding low alloy steel, such as the so-calledT'steel, wtihout involving the use of coated. stick electrodes or aflux-submerged arc.

it is a further object of the instant invention to provide an improvedinert-gas-shielded metal arc welding n ethod for certain low alloysteels and an improved wire composition adapted to be used in suchmethod whereby high-mechanical-strength welds which are highly resistantto impact are obtained in the as-welded condition.

After much experimentation and many difiiculties, a welding wirecomposition was discovered which proved eminently suitable for effectingwelds with low alloy steels, such as armor plate and T-stecl.Preferably, this wire is used in a modified inert-gas-shiel-ded, metalare method of welding. The wire composition by percent weight analysisis from about .04 to about .08 carbon; from about 1.20 to about 1.50manganese; from about .30 to about .60 silicon; from about .10 to about.20 vanadium; from about 1.10 to about 1.30 nickel; from about .30 toabout .55 molybdenum; .025, maximum, phosphorus; .025, maximum, sulfur;.15, maximum, chromium; .035 maximum, titanium; and the remainder beingessentially iron. Residual elements, such as copper, tin and lead shouldbe kept as low as possible, such as less than .20%. The wire has a cleansurface, that is, free of drawing compounds and preferably thiscondition is obtained by cleaning. Before this cleaning, a copper filmis preferably put on the surface. The copper film is obtained by meansof a copper sulphate bath. The heat from which the wire is made issilicon-killed (deoxidized with silicon) without the use of aluminum, sothat a Wire which is devoid of residual aluminum due to aluminumdeoxidizing results. Aluminum from other sources may be detected but isvery small in amount, such as 006%, as hereinafter noted. It is to benoted that the wire contains at least iron.

An example of apparatus suitable for utilizing the instant wire and ofthe basic method of using the wire is disclosed in Muller et al. PatentNo. 2,504,868, issued April 18, 1950, assigned to applicants assignee.This patent discloses the recently-developed inert-gas-shielded, metalarc welding method which was modified in developing the instant process.

With the above-described wire, it became possible to make improved armorweldments, using the basic steps of the inert-gas-shielded metal arcwelding method above mentioned. These weldments met militaryspecifications for armor and hence had high yield strength (exceeding90,000 pounds per square inch) and high resistance to impact. Theresistance to impact resulted, in part, from the fact that theinert-gas-shielded metal arc welding process inherently does not involvewater contamination or other factors conducive to cracking since no fluxor flux coating is used. Once the problem of discovering a wirecomposition which will work in the above-mentioned type of weldingprocess and give the desired tensile strength without other adverseeifects, the inherent avoidance of flux and water contamination results.It is to be appreciated that innumerable complications were involved indiscovering a suitable wire. Among the important factors are thecomposition of the wire and the material to be welded, the shieldinggas, the type of current and/ or are polarity, and the relation of thearc, the alloying elements, the wire and the workpiece. The preferredwelding conditions for low alloy steels including armor plate andT-steel include the use of reverse-polarity direct current, a 99%argon-1% oxygen, non-turbulent gas shield and a wire feed of at least100 inches per minute.

With the instant invention, the advantages of a higher rate ofdeposition of a weld which can be used as welded without heat treatmentand a high yield strength Weld 3 which is not subject to cracking in theheat-aifected zone of the weld are achieved. It is to be realized thatthe instant welds are not to be stress relieved after Welding since theweld zone would become embrittled. It is to be appreciated that theinstant welds at least match the yield strength of the workpieces whichthe welds join.

In welding one type of armor plate (ordnance armor) the averagecomposition of the instant ferritic wire having the above range ofcomposition was by weight percent, carbon .07; phosphorus .014; sulfur.012; silicon. .40; manganese 1.45; nickel 1.15; molybdenum .47;vanadium .17; chromium .12; titanium .034; aluminum .006; and theremainder being essentially iron containing residual traces of otherelements.

Typical welding conditions for welding one and one half inch ordnancearmor plate with the instant wire were as follows:

Electrode diameter: inch Gas: 99% argon-1% oxygen at 40 cubic feet perhour Power: reverse polarity direct current Current: 305310 amperes Arcvoltages: 27-30 volts Travel speed per pass: 9-12 inches per minute Wirefeed rate: 180-250 inches per minute The composition of the plate whichwas used in the above-described welding operation was, by weight percentanalysis, carbon .25; manganese 1.17; silicon .46; phosphorus .013;sulfur .022; chromium .66; nickel .61; molybdenum .33; and the remainderbeing essentially iron. No zirconium or vanadium was detected. Thechemical composition of the weld metal on the same percent basis was,carbon .07; manganese 1.09; silicon .26; sulfur .017; phosphorus .013;chromium .18; nickel 1.15; molybdenum .44; vanadium .16; and theremainder being essentially lIOIl.

The typical mechanical properties for the weld metal was: yield strength101,000 pounds per square inch, and tensile strength 114,000 pounds persquare inch. The impact strength test, as made on a weld-metal Charpytype specimen with an Izod notch, showed resistance to impact at about55 foot pounds at about 40 F. Military specification (MIL-E-986A Grade230) was met by the above-described welds.

The compositions of other typical ordnance armor plates are as follows:

Armor Plate [Mn Si Or The instant wire and methods are suitable forwelding the above armor. It is to be noted, in respect to the armormaterial, that the carbon is less than 30% but more than .15 and thatthe alloying elements comprise less than but more than 2% and includeprincipally manganese, silicon, chromium, nickel and molybdenum. Bynoting the composition of T-steel hereinafter, it can be seen thatT-steel has a similar composition in respect to most of the alloyingelements. The small amount of boron in the above armor steelscontributes significantly to the hardenabi'lity of these steels.

The above-mentioned T-steel has a composition by percent weight analysisof carbon .18, maximum; manganese .801.20; silicon ISO-.50; nickel.701.00; molybdenum .35-.60; vanadium .03 minimum; copper .20-.40;chromium .35.60; boron .003; sulfur .035; phosphorus .035; aluminum .07;titanium .006; and the remainder iron. It is to be noted that theprincipal alloying elements, manganese, silicon, nickel, molybdenum andchromium, in this steel (low carbon less than 30%) constitute lessflilan 5% but more than 2%, as was the case with armor p ate.

In welding T-steel, the wire composition was as abovedescribed. Thepreferred gas shield and current are argon gas with 1% oxygen additionand reverse-polarity direct current, which are the same as the preferredconditions for armor welding.

A typical single V butt-weld joint, as deposited and made with both oneinch and one-half inch T-steel plates and the instant wire, had atransverse tensile strength of 120,100 pounds per square inch. Thelongitudinal yield tensile strength of this joint was 103,000 pounds persquare inch. This joint was made with ,4 inch diameter wire and a 99%argon plus 1% oxygen gas shield. The voltage was about 27 volts and thecurrent was about 360 amperes. The travel speed was about 10 inches perminute. The wire feed was about inches per minute. Charpy keyholeproperties of the above joint as welded were 50% chear at about 118 F.and 20 foot pounds at -129 F.

Typical tensile properties of weld metal made in'connection with T-steelwere yield strength 105,900pounds per square inch and tensile strength113,400 pounds per square inch. This weld metal had a percent weight analysis of carbon .07; manganese 1.11; phosphorus 0.17; sulfur .015;silicon .30; nickel 1.19; chromium .11; molybdenum .40; vanadium .09;copper .29; and titanium .008.

Another type of low alloy steels which can best be welded with the novelelectrode wire of the present invention used with the inert gas shieldedmetal are welding process are the so-called Special Treatment Steels,more commonly known as STS steels, used largelyin ship building,particularly in the construction of combat vessels. These steels arealso classified as armor and form the basis of Military Specification 47S 26. Basically STS steel is a low alloy steel having manganese,chromium and nickel as the principal alloying elements. While themilitary specification for STS steel does not specify a chemicalanalysis, steels made to conform to the specification have as a rule apercent weight analysis that falls within the following range: carbon.23-.30; manganese .20.60; silicon .03-.30; chromium .80+1.50; nickel2.5 0-4.00; molybdenum .03-.20. A specific sample of STS steel waswelded in accordance with the present invention. The welding electrodewire used was inch in diameter of the same novel composition asheretofore described. The inert gas shielded metal arc welding processwas used. The welding conditions were:

Current: 300 amperes, direct current reverse polarity Arc voltage: 28volts Wire feed: 210 inches per minute Shielding gas: 40 cubic feet perhour of argon plus 1% oxygen The weld so made fully met the mechanicalproperty requirements of specification MILE-986A.

From the foregoing, it is apparent that an improved wire composition andan improved preferred process using such wire have been discovered whichare adapted for the welding of certain high strength low alloy steels,such as armor plate and T-steel. These steels and other comparablesteels can be defined as low alloy, high strength steels having .15-.30%carbon and 2-5% other alloying elements. The other alloying elementscomprise principally manganese, silicon, chromium, nickel andmolybdenum, and may include other elements such as boron or vanadium.Such low alloy steels usually contain alloying elements in substantiallythe following percentages by weight of the total alloy; manganese.20-l.50; silicon .03- .70; chromium .04-1.50; nickel .054.00;molybdenum .03-.60. The remainder of the steel is substantially iron,although it may contain small amounts of such elements as copper, tin,lead, boron, titanium andvanadium. The

instant wire and process can be used to weld this type of steel.

In the foregoing examples and in the practice of this invention,it'istobe' understood that'the electric welding are can be described asbeing rooted to a workpiece and that the workpiece is preferablynegative in respect to the electrode, so that the above-mentioned directcurrent at reverse polarity results. In welding, a clean bare weldingwire (one which is not flux coated) is fed to the arc and forms the weldpool which, along with the tip of the wire, is shielded or blanketed byan inert-gas-shield. It is preferred that the instant wire be used as aconsuming electrode wire; that is, the arc roots thereon and theelectrode is sprayed or transferred to the workpiece and hence consumed.It is also preferred that the inert-gas-shield be 99% argon and 1%oxygen for welding the above-described low alloy steels. The usual endresult of the instant invention is a weldment comprised of at least twopieces of the certain low alloy steels which are joined by a ferrousweld deposit derived from the instant wire by the above preferredconditions. It is apparent that the instant invention can be utilized tofill defects and to do overlay work and similar operations. It is alsoto be understood that, in practice, the instant wire is sold and used asa coil of welding wire adapted to be fed to an electric arc.

The exact explanation of why the instant wire and proccess produces aweldment which has both high yield strength and a high resistance toimpact is not known. However it has been found that the instantferritic-type electrode does result in welds which have the desiredyield strength and which avoid the problem of underbead cracking.Military requirements as to ballistic loading on armor plate have beenmet. Similar considerations apply to welded T-steel constructions, suchas pressure vessels and rolling stock and similar results have beenobtained.

It is to be appreciated that greater speed of welding results with theinstant wire and process and hence greater overall economy is effectedthan is possible with stick electrode welding. The use of appreciableamounts of expensive and critical materials, as is required forstainless steel stick electrodes, is avoided. The special precautionsrequired for coated ferritic-type stick electrodes are also avoided.

While the preferred embodiments of the invention have been described, itis to be understood that one skilled in the art can make otherembodiments within the scope of the following claims.

We claim:

1. The method of welding a ferrous metal workpiece comprised of, byweight, .15% to 30% carbon; about 2-5% of other alloying elementsresulting from the incorporation of about .80% to 1.50% manganese; .22%to .70% silicon; .04% to .95% chromium; .O5% to 1.00% nickel; .l7% to.60% molybdenum and the remainder being substantially iron; said methodcomprising establishing a direct current reverse polarity electric arebetween said ferrous metal workpiece and consumable ferrous electrodecontaining, by weight, .04% to .08% carbon; 1.20% to 1.50% manganese;30% to .60% silicon; 1.10% to 1.30% nickel; .10% to .20% vanadium; and30% to .55 molybdenum; blanketing said arc, the consurning end of saidelectrode, and the welding pool formed on said workpiece with anon-turbulent stream of 99% of argonl% oxygen gas to exclude air fromsaid pool and said consuming end; and advancing said electrode tomaintain the arc, as electrode material is transferred from theelectrode to said metal, so that a weld having a high yield strength andbeing resistant to impact is formed.

2. The method of welding low allow steels containing, by weight, about.15% to 30% carbon and about .80% to 1.50% manganese; .22% to .70%silicon; .04% to .95% chromium; .05% to 1.00% nickel; .17% to .60%molybdenum, with the total of said elements being between 25%, saidmethod comprising rooting an electric welding arc to a workpiece of saidsteel and feeding a bare welding wire to said arc, said welding wirebeing a ferrous alloy containing, by weight, .04% to .08% carbon; 1.20%to 1.50% manganese; 30% to .60% silicon;

.10% to .20% vanadium; 1.10% to 1.30% nickel, and 30% to .55 molybdenum.

3. The method of welding a low alloy steel containing, by weight, about.15 to 30% maximum, carbon; .80% to 1.20% manganese; 30% to .50%silicon; 35% to .60% chromium; .70% to 1.00% nickel; 35% to .60%molybdenum, said method comprising rooting an electric welding arc to aworkpiece of said steel and feeding a bare Welding wire to said arc,said welding wire being a ferrous alloy containing, by weight, .04% to.08% carbon; 1.20% to 1.50% manganese; 30% to 60% silicon; .10% to .20%vanadium; 1.10% to 1.30% nickel; and 30% to .55% molybdenum.

4. The method of welding armor plate having compositions, by weight, of.25% to .28% carbon; .90% to 1.50% manganese; .22% to .70% silicon; .04%to .95% chromium; .05% to .90% nickel; .l7% to .35% molybdenum, with thetotal of said elements being between about 2-5%, said method comprisingrooting an electric welding arc to a workpiece of armor plate havingsaid composition and feeding a bare welding Wire to said are, Saidwelding wire being a ferrous alloy containing, by weight, .04% to .08%carbon; 1.20% to 1.50% manganese; 30% to .60% silicon; .10% to .20%vanadium; 1.10% to 1.30% nickel; and 30% to .55% molybdenum.

5. The method according to claim 4 and being further characterized inthat the armor plate contains from 002% to 003% boron.

6. A ferritic-type weld wire for welding low alloy steels containing, byweight, about .15% to 30% carbon; and about .80% to 1.50% manganese;.22% to .70% silicon; .04% to .95 chromium; .05% to 1.00% nickel; and.l7% to .60% molybdenum, with the total of said elements being between2.00% to 5.00%; said wire being fed to an electric are which is shieldedfrom the atmosphere by an inert gas, said wire containing by percentageWeight analysis, carbon 04% to .08%; manganese 1.20% to 1.50%; silicon.30% to .60%; nickel 1.10% to 1.30%; vanadium .10% to .20%; molybdenum30% to .55%; and the remainder being essentially iron.

7. A ferritic-type welding wire for gas shielded arc welding of highstrength low alloy steel, said wire containing by weight of the totalalloy from about .04% to about .08% carbon; from about 1.20% to about1.50% manganese; from about 30% to about .60% silicon; from about 1.10%to about 1.30% nickel; from about .10% to about .20% vanadium; fromabout 30% to about .55 molybdenum, and the remainder substantially alliron.

8. A ferritic-type welding wire for gas shielded arc welding highstrength low alloy steels containing by weight, about .15% to 30% carbonand from 2% to 5% of alloying elements comprising principally manganese,silicon, chromium, nickel, and molybdenum, said wire containing byWeight of the total alloy from about .04% to about .08% carbon, fromabout 1.20% to about 1.50% manganese, from about 30% to about .60%silicon, from about 1.10% to about 1.30% nickel, from about .10% toabout .20% vanadium, from about 30% to about .55% molybdenum, and theremainder substantially all iron.

9. A ferritic-type welding wire for gas shielded arc welding highstrength low alloy steels containing by weight about .15% to 30% carbon,and about .20% to 1.50% manganese, .03% to .70% silicon, .04% to 1.50%chromium, .05% to 4.00% nickel, and .03% to .60% molybdenum, with thetotal of said alloying elements being between 2.00% and 5.00%; said wirecontaining by percentage weight analysis, carbon .04% to .08%, manganese1.20% to 1.50%, silicon 30% to .60%, nickel 1.10% to 1.30%, vanadium.10% to .20%, molybdenum 30% to .55%, and the remainder beingessentially iron.

10. The method of welding low alloy steels containing by weight about15% to 30% 'cfarboiiandalioiii 20% to 1.50% manganese, .03% f0 .70%'silicon, .04% to 1.50% chromium, 05% to 4.00% nickel, 03% to .60% 1molybdenum, with the total of said alloying elenients being between 2%and 5%, said method comprising rooting an electric welding arc to 'aworkpiece of said Refereii'c'esfited in the file of this patent .UNITEDSTATES PATENTS Austin 'Ndv. 26, 1935 Strauss May 12, I936 'Rooke Aug.26, '1941

1. THE METHOD OF WELDING A FERROUS METAL WORKPIECE COMPRISED OF, BYWEIGHT, .15% TO .30% CARBON; ABOUT 2-5% OF OTHER ALLOYING ELEMENTSRESULTING FROM THE INCORPORATION OF ABOUT .80% TO 1.50% MANGANESE; .22%TO .70% SILICON; .04% TO .95% CHROMIUM; .05% TO 1.00% NICKEL; .17% TO.60% MOLBDENUM AND THE REMAINDER BEING SUBSTANTIALLY IRON; SAID METHODCOMPRISING ESTABLISHING A DIRECT CURRENT REVERSE POLARITY ELECTRIC ARCBETWEEN SAID FERROUS METAL WORKPIECE AND CONSUMABLE FERROUS ELECTRODECONTAINING, BY WEIGHT, .04% TO .38% CARBON; 1.20% TO 1.50% MANGANESE;.30% TO .60% SILICON; 1.10% TO 1.30% NICKEL; .10% TO .20% VANADIUM; AND.30% TO .55% MOLYBDENUM; BLANKETING SAID ARC, THE CONSUMING END OF SAIDELECTODE, AND THE WELDING POOL FORMED ON SAID WORKPIECE WITH ANON-TURBULENT STREAM OF 99% OF ARGON-1% OXYGEN GAS TO EXCLUDE AIR FROMSAID POOL AND SAID CONSUMING END; AND ADVANCING SAID ELECTRODE TOMAINTAIN THE ARC, AS ELECTRODE MATERIAL IS TRANSFERRED FROM THEELECTRODE TO SAID METAL, SO THAT A WELD HAVING A HIGH YIELD STRENGTH ANDBEING RESISTANT TO IMPACT IS FORMED